Risk assessment and mitigation of water quality systems: recoverable and non-recoverable responses to failure

在自然环境和人工环境中，维持水质目标可能受到以下因素的影响：可观察到的事件或输入，如水流的变化；不可观察到的事件或输入，如机械故障；以及我们对控制这些系统的因果关系的有限理解。这些输入在本质上可能是平稳的，随时间具有恒定的平均值和标准偏差，或者是非平稳的，表现出随时间统计特性的变化，例如由于气候变化。在任何情况下，对规划和操作决策的预期水质反应可能是非常多变的，未能达到水质目标可能是严重的，而这种失败的后果可能是可修复的，即发生故障后可以正常工作，也可能是不可修复的，不能正常工作。在不同领域为保护水质而作出的决定类型可能有所不同；然而，绩效目标是相似的，重点是尽可能可靠地达到水质标准。该项目发展分析技术，包括确定可靠性和其他性能措施，以评估有关河流水质和供水系统的决定。该项目将：1)在系统输入是非平稳的情况下，推进可修复河流水质管理系统的性能测量方法的使用。制定和应用识别适应不断变化的投入条件的规划决策的方法；2)开发和研究绩效指标的使用，以评估何时升级配水系统要素；3)制定评估方法和实践，以提高水处理技术的可靠性，以实现健康目标。

Maintenance of water quality objectives in natural and constructed environments may be affected by events or inputs that are observable, such as variations in streamflow, and by those that are unobservable, such as mechanical failures, and by our limited understanding of the cause and effect relationships that govern such systems. The inputs may be stationary in nature, having a constant mean and standard deviation over time, or non-stationary, exhibiting changes in the statistical properties over time, due, e.g., to climate change. In any case, the expected water quality response to planning and operational decisions may be quite variable, failure to meet water quality objectives may be severe, and the consequences of such failures may be repairable, i.e., functioning, or non-repairable, not functioning, after failures occur. The types of decisions undertaken to protect water quality in different domains may differ; however the performance objectives are similar and focus on achieving water quality standards as reliably as possible. This project develops analytical techniques, including identification of reliability and other performance measures, for evaluating decisions regarding river water quality and water supply systems. This project will: 1) advance the use of performance measures for repairable river water quality management systems in cases where the system inputs are non-stationary. Methods for identifying planning decisions that adapt to changing input conditions will be developed and applied; 2) Develop and investigate the use of performance measures for evaluating when to upgrade water distribution system elements; and 3) Develop methods for estimating and practices for enhancing the reliability of water treatment technologies for meeting health targets.